Sheet feed mechanism



Aug. 10, 1965 R, H. EICHORN ETAL 3,199,366

SHEET FEED MECHANISM Filed May 24, 1963 3 Sheets-Sheet l INVENTOR.R'OGER H. EICHORN DONALD L. PEASLJR.

A 7' TORNE V Aug. 10, 1965 R. H. EICHORN ETAL 3,199,365

SHEET FEED MECHANISM Filed May 24, 1963 3 Sheets-Sheet 2 INVENTOR. ROGERH. EICHORN BY DONALD L. PEASE,JR.

A TTOR/VE Y R. H. EICHORN ETAL 3,199,866

SHEET FEED MECHANISM 3 Sheets-Sheet 3 amxm INVENTOR. ROGER H. EICHORN BDONALD L.PEASE,JR. "Mn/M ATTORNEY Aug. 10, 1965 Filed May 24, 1963United States Patent 3,199,866 SHEET FEED MECHANISM Roger H. Eichoru,Webster, and Donald L. Pease, Jr.,

Marion, N.Y., assignors to Xerox Corporation, Rochester, N.Y., acorporation of New Yorlr Filed May 24, 1963, Ser. No. 282,952 3 Claims.(Cl. 271-79) This invention relates in general to a sheet feed mechanismand, in particular, to a sheet conveyor mechanism got seriatim feedingof sheet material to a xerographic rum.

Specificall the invention relates to an improved sheet grippermechanism, of the type disclosed in copending Roger H. Eichornapplication, Serial No. 77,956, filed December 23, 1960, now Patent No.3,100,109, for a sheet conveyor that is particularly adapted for use ina xerographic reproducing apparatus, and which is also suitable for usewith comparable types of devices.

In the process of xerography, for example, as disclosed in eitherCarlson Patent 2,297,691, issued October 6, 1942, or in Carlson Patent2,357,809, issued September 12, 1944, a xerographic plate, comprising alayer of photoconductive insulating material on a conductive backing, isgiven a uniform electrostatic charge over its surface and is thenexposed to the subject matter to be reproduced, usually byconventionalprojection techniques. This exposure discharges the plateareas in accordance with the radiation intensity which reaches them andthereby creates an electrostatic latent image on or in the platecoating.

Development of the image is effected with developer material ordevelopers which comprise, in general, a mixture of a suitable pigmentedor dyed electroscopic powder, hereinafter referred to as toner, and agranular carrier material, which latter functions to carry and togenerate triboelectric charges on the toner. More exactly, the functionof the granular material is to provide the mechanical control to thepowder, or to carry the powder to an image surface and, simultaneously,to provide almost complete homogeneity of charge polarity. In thedevelopment of the image, the toner powder is brought into surfacecontact wtih the xerographic plate and is held thereon electrostaticallyin a pattern corresponding to the electrostatic latent image.Thereafter, the xerographic powder image is transferred to a supportmaterial to which it may be fixed by any suitable means.

The invention relates to conveyors and in particular to sheet grippermechanism for conveying sheet material, such as paper or the like, tocontact the xerographic plate in synchronized movement therewith wherebythe developed xerographic image from the xerographic plate istransferred in proper registration onto the sheet material.

Because of cost and other considerations, it is desirable to use in thesheet conveyor, roller chains having relatively small diameter rollers.It is also desirable to have the sheet grippers carried by the rollerchains of a minimum thickness, preferably of a thickness correspondingto the thickness of the roller chains.

It is apparent that the sheet gripper elements cooperat ing with eachother to grip a sheet must be biased into cooperative engagement tosecurely grip the sheet. Because this biasing force can be relativelylarge whereas the thickness of the individual sheet gripper elements isrelatively small, the sheet gripper elements can readily be twisted ordeflected as the sheet gripper is caused by cam action to open toreceive or reject sheet material.

It is therefore the principal object of this invention "to improve sheetfeeding mechanisms for use in a xerographic apparatus or similar device.

A further object of this invention is to improve sheet gripper devicesand their actuators to sheet gripper devices to securely grip sheetmaterial without deflection of the sheet gripper elements.

Another object of this invention is to improve sheet gripper devices foruse in a sheet conveyor whereby various sized sheet material can beconveyed.

These and other objects of the invention are attained by means of asheet conveyor including two endless belts, in the form of rollerchains, supported by pulley means for travel in unison in two spacedsubstantially parallel planes to transport a sheet gripper mechanismfrom a sheet receiving station to a sheet delivery station. The sheetgripper mechanism includes a gripper bar connected to the endless beltsalong a line perpendicular to the spaced planes of travel of the endlessbelts. The gripper bar supports sheet gripping means including at leastone movable gripper having a jaw adapted to cooperate with the jaw of asecond gripper to grip a sheet therebetween. Pairs of cam means arelocated adjacent and between the endless belts at the sheet receivingstation and the sheet delivery station. For a better understanding ofthe invention as well as other objects and further features thereof,reference is had to the following detailed description of the inventionto be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a xerographic reproducingapparatus having a sheet feed mechanism using a preferred embodiment ofa sheet gripper mechanism of the invention;

FIG. 2 is a perspective view of the sheet feed mechanism of theapparatus of FIG. 1;

FIG. 3 is a top view of a preferred form of paper gripper mechanismconstructed in accordance with the invention;

FIG. 4 is an enlarged view of the paper gripper taken along line 4-4- ofFIG. 3;

FIG. 5 is an enlarged view taken along line 5-5 of FIG. 3;

FIG. 6 is an enlarged view taken along line 66 of FIG. 3;

FIG. 7 is an enlarged view taken along line 7-7 of FIG. 3; and

FIG. 8 is an enlarged exploded view in perspective of a .portion of thepaper gripper mechanism.

charge is deposited on the photoconductive layer of the xerographicdrum;

An exposure station, at which a light or radiation pattern of copy to bereproduced is projected onto the drum surface to dissipate the drumcharge in the exposed areas thereof and thereby form a latentelectrostatic image of the copy to be reproduced;

A developing station, at which a xerographic developing materialincluding toner particles having an electrostatic charge opposite tothat of the electrostatic latent image are cascaded over the drumsurface, whereby the toner particles adhere to the electrostatic latentimage to form a xerographic powder image in the configuration of thecopy to be reproduced;

A transfer station, at which the xerographic powder image iselectrostatically transferred from the drum surface to a transfermaterial or support surface; and,

A drum cleaning station, at which the drum surface is first charged andthen brushed or wiped to remove residual toner particles remainingthereon after image transfer, and at which the drum surface is exposedto a relatively bright-light source to effect substantially completedischarge of any residual electrostatic charge remaining thereon.

The charging station is preferably located as indicated by referencecharacter A in the schematic illustration of the apparatus. In general,the charging apparatus or corona charging device 21 includes a coronadischarge array of one or more discharge electrodes that extendtransversely across the drum surface and are energized from a highpotential source and are substantially enclosed within a shieldingmember.

Next subsequent thereto in the path of motion of the xerographic drum isan exposure station B provided with an optical scanning or projectionsystem to project a flowing image of a document onto the photoconductivesurface of the xerographic drum from a suitable original.

The optical scanning or projection assembly consists of a copyboard inthe shape of a drum, hereinafter referred to as copy drum 30, which isadapted to support copy to be reproduced and arranged to rotate in lightprojection relation to the moving light-receiving surface of thexerographic plate. Uniform lighting is provided by suitable lamps 31attached to a slotted light reflector 32 mounted adjacent to the copydrum.

A slotted light shield 33, adapted to protect the xerographic plate fromextraneous light, is positioned adjacent to the surface of thexerographic plate. A slot aperture in the light shield extendstransversely to the path of movement of the light-receiving surface ofthe xerographic drum to permit reflected rays from the copy drum to bedirected against a limited transverse area of the light-receivingsurface as it passes thereunder.

To enable the optical system to be enclosed within a relatively smallcabinet, a folder optical systemlincluding an object mirror 34, a lens35, and an image mirror 36, is used in the preferred embodiment of theapparatus.

A document fed through document guides 37 to the copy drum is removablysecured thereon by a suitable gripper mechanism for movement therewithin timed relation to the movement of the xerographic drum whereby aflowing image of the copy is projected onto the xerographic drum. Thecopy is held against the surface of the copy drum until gripped by meansof document retaining guides 38. Pressure guides 39 and document guard41 retain and guide the trailing edge of the document on the copy drum.After the copy is scanned, it is released from the copy drum to betransported out of the machine by the copy drum and document feed outrollers 42 through document feed out guide 43.

Adjacent to the exposure station is a developing station C in whichthere is positioned a developer apparatus 50 including a developerhousing having a lower or sump portion for accumulating developermaterial 51. Mounted within the developer housing is a drivenbucket-type t conveyor 52 used to carry the developer materialpreviously supplied to the developer housing to the upper portion of thedeveloper housing from where the developer material is cascaded over ahopper chute 53 onto the drum.

As the developer material cascades over the drum, toner particles of thedeveloper material adhere electrostatically to the previously formedelectrostatic latent image areas on the drum to form a visiblexerographic powder image; the remaining developer material falling offthe peripheral surface of the drum into the bottom of the developerhousing. Toner particles consumed during the developing operation toform the xerographic powder images are replenished by a toner dispenser54, mounted within the developer housing.

Positioned next adjacent to the developing station is the image transferstation D which includes suitable sheet feeding mechanism adapted tofeed sheets of paper successively to the xerographic drum incoordination with the presentation of the developed image on the drum atthe transfer station. The sheet feeding mechanism includes a sheetsource such as paper tray 69 for a plurality of sheets of a suitablesupport material, that is, sheets of paper or the like, separatorrollers 61 adapted to feed the top sheet of the stack of supportmaterial through a guide 67 to a sheet conveyor mechanism 62 havingsheet gripper mechanisms 63 thereon which carry the sheet supportmaterial into contact with the rotating xerographic drum in coordinationwiththe appearance of a developed image at the transfer station.

The transfer of the xerographic powder image from the drum surface tothe support material is effected by means of a corona transfer device 64that is located at or immediately after the point of contact between thesupport material and the rotating xerographic drum. The corona transferdevice 64 is substantially similar to the corona discharge device thatis employed at the charging station in that it also includes an array ofone or more corona discharge electrodes that are energized from asuitable high potential source and extend transversely across the drumsurface and are substantially enclosed with a shielding member. Inoperation, the electrostatic field created by the corona transfer deviceis effective to tack the transfer material electrostatically to the drumsurface and simultaneously with the tacking action, the electrostaticfield is effective to attract the toner particles comprising thexerographic powder image from the drum surface and cause them to adhereelectrostatically to the surface of the support material.

As the paper gripper mechanism continues to move forward in its closedcircuit, it will strip the support material from the xerographic drumand carry it to a fixing device, such as, for example, heat fuser 7i),whereat the developed and transferred xerographic powder image on thesupport material is permanently fixed thereto.

After fusing, the finished copy is preferably discharged from theapparatus at a suitable point for collection externally of theapparatus. To accomplish this, there is provided a pair of deliveryrollers 65 and 66 by means of which the copy is delivered from themachine after it is released by the gripper mechanism. Suitable cammeans 68 and es are provided at the receiving and delivery stations ofthe conveyor mechanism, respectively, to actuate the paper grippers ofthe sheet gripper mechanisms at these stations to receive or discharge asheet of support material.

The next and final station in the device is a drum cleaning station Ewhereat any powder remaining on the xerographic drum after the transferstep is removed and whereat the xerographic drum is flooded with lightto cause dissipation of any residual electrical charge remaining on thexerographic drum.

To aid in the removal of any residual powder remaining on thexerographic drum, there is provided a corona precleaning device 84 thatis substantially similar to the corona discharge device that is employedat charging station A. Removal of residual powder from the xerographicdrum is effected by means of a web cleaner device 80 adapted tocontinuously feed a clean fibrous web material into wiping contact withthe xerographic drum. As shown, the web material is taken from a supplyroll 81 and transported around a cleaning or pressure roll 82,preferably made of rubber, onto a take-up or rewind roll 83.

Any residual electrical change remaining on the xerographic drum isdissipated by light from the fluorescent lamp 85 mounted in a suitablebracket above the xerographic drum, a suitable starter and ballast beingprovided for energizing the fluorescent lamp.

Suitable drive means drive the xerographic drum, the copy drum, thesheet conveyor mechanism at predetermined speeds relative to each other,and to efiect operation of the paper separator roll, and the web cleanermechanism, the latter being driven at a speed or speeds whereby relativemovement between the xerographic drum and the web material is efiected.Suitable drive means are also provided for efiecting operation of theconveyor mechanism and toner dispenser of the developing apparatusassembly.

It is believed that the foregoing description is sufiicient for thepurposes of this application to show the general operation of thexerographic reproducing apparatus. For further details concerning thespecific construction of the xerographic reproducing apparatus,reference is made to copending Eichorn et al. application, Serial No.162,779, now Patent No. 3,099,943 filed December 28, 1961, and toportions of this specification wherein specific elements cooperatingwith the sheet feed mechanism are illustrated and described althoughthey form no part of the instant invention.

Referring now to the subject matter of the invention, the sheet conveyormechanism 62 includes two endless belts, in the form of roller chains321, which extend from a set of drive sprockets 322 carried by shaft 8H3to, and around, a set of sprockets 323 on shaft 81-14. These two sets ofsprockets are fixedly positioned on their respective shaft to space theroller chains apart from each other by a distance greater than thelength of the drum to afford complete use of the xerographic drumsurface.

In the embodiment of the sheet conveyor mechanism shown, the rollerchains carry two sheet gripper mechanisms. The sheet gripper mechanisms63 are equally spaced from each other along the length of the chains,and are positioned on the chains at right angles to the path of travelof the chains for movement therewith in a circuit between sheetreceiving and sheet delivery stations, identified as the output area ofthe paper guide 67, and the delivery rollers 65 and 66, respectively.Suitable cam elements 68 and 69 are provided at these stations toactuate the sheet gripper mechanisms.

Two paper grippers are used in the machine shown so that as one sheetgripper mechanism is moved from the receiving station carrying sheetmaterial to the delivery station, the other sheet gripper mechanism willadvance from the delivery station to the receiving station to be inposition to receive the next sheet from paper guide 67. For furtherdetails concerning the specific construction of the sheet feedingmechanism of the xerographic reproducing apparatus, reference is made tothe referenced copending Eichorn et al. application, Serial No. 162,779.

Referring now to the subject matter of the invention, there is shown inFIGURES 3-8, inclusive, a preferred embodiment of the sheet grippermechanism of the invention.

As shown, each sheet gripper mechanism 63 includes a gripper bar 35% ofa length to extend substantially between the two roller chains 321 to beconnected thereto by means of clips 354 forming part of the chains whenconnected thereto, as is well known in the art. The gripper 6 barincludes a gripper bar bracket 351 and a sheet gripper jaw 355 formed sothat the top surface of the gripper bar is positioned tangentially to orslightly below the pitch line of the chains, whereby the gripper bar asit passes beneath the Xerographic drum will not jam against theperipheral surface of the xerographic drum.

A sheet gripper jaw 355, which may be a separate element fixed to thegripper bar bracket, as shown, or formed integral therewith, extendsacross the rear of the gripper bar bracket (in terms of the direction oftravel of the gripper bar). The sheet gripper jaw 355 is positioned tohave surface contact with the leading edge of a sheet of supportmaterial as it advanced from the paper guide 67. The sheet gripper jawcooperates with the tang portions of jaws 362 of the grippers 361 togrip a sheet of support material inserted therebetween. Preferably, thesheet gripper jaw 355 is provided at its trailing 'edge (in terms of thedirection of travel), with a concave shape cutout 358 with which thetang portions or jaws 362 cooperate to slightly bend the leading edge ofa sheet gripped therebetween.

Each of the grippers 361 is mounted, by means of pins 371 suitablysecured to the pin retaining portions 358 on the leading edge of thegripper bar bracket, for movement in two directions relative to thefixed sheet gripper jaw 355; that is, for movement from a first positionin which the tangs or jaws of the gripper are in spaced relation to thesheet gripper jaw to receive a sheet of support material therebetween,and for movement to a second position in which the tangs or jaws of thegripper are in engagement with the sheet gripper jaw or with a sheet ofsupport material sandwiched therebetween.

Each gripper is provided with a depending guide portion or tang 363terminating in a curved-lip portion 364 which is slidably received insuitable elongated slots 356 and 352 formed in the sheet gripper jaw andgripper bar bracket, respectively. The guide portion or tang 363 servesas a guide or stop for the leading edge of a sheet and, also as anactuating lever by means of which the gripper is actuated. Each gripperis also provided with a central bent arm or spring tang 373 received inthe notched or secured portion 372 of a pin 371. The central bent arm orspring tang of the gripper and the recess 372 in the pin 371 serve adual function. They accurately restrain and retain the gripper and thepin relationship to gripper and, this arrangement permits quick andreliable changing of parts.

The tang portion or jaw 362 of a gripper 361 are normally biased intocontact with the sheet gripper jaw 355 or with a sheet therebetween bymeans of a spring 365. Each spring 365 is formed with a central portion367, coiled portion 366 on the opposite sides of the central portion andwith bent arms 368 at opposite extremities, thereof. Each spring ismounted with its coiled portion 366 encircling a pin on opposite sidesof the gripper with which it cooperates, the central portion of thespring engaging the curved lip portion 364 of the gripper 361 and withthe bent arm portions extending through suitable apertures 357 and 353in the gripper jaw and gripper bar bracket, respectively, to engage theunderside of the the gripper bracket.

Referring now to FIG. 1, a sheet of support material, such as paper,forwarded into the paper guide 67 by the action of the separator rollers61 is buckled as the separator rollers continue to advance the sheetafter forward motion has been arrested by the gate of the paper guide.Thus, as a paper gripper advances over the guide, the gate will beforced open as the paper gripper strikes it and, at the same time, thecam follower of the sheet gripper mechanism, that is, the dependingguide portion or tang 363 of each of the sheet grippers will strike thecam assembly 68 secured adjacent to the gate of the paper guide. As thecam follower of the sheet gripper mechanism contacts the cam assembly,the jaws of the individual paper grippers will be open to receive thesheet from the paper guide. Because of the slight buckle in the sheetand because at this time the separating rollers are still attempting toadvance the sheet, the sheet as it unbuckles will be forced between thejaws of the paper gripper. As the depending guide portion and curved lipportion of the grippers slide off earns 68, the jaws will close by thebiasing action of springs 365 to grip the sheet.

At the delivery station, the sheet gripper mechanism passes between thedelivery rollers 65 and 66 and as it does so, the grippers are againactuated by means of a cam 69 thereby releasing the sheet from the sheetgripper mechanism for discharge from the machine.

In operation, the electrostatic field created by the corona transferdevice 64 is effective to tack the support material electrostatically tothe drum surface, whereby the support material moves synchronously withthe drum while in contact therewith. As the sheet gripper mechanism,carrying the sheet of support material, moves away from the Xerographicdrum to the delivery station, it pulls the sheet away from the surfaceof the drum, against the electrostatic forces tending to retain thesupport material to the drum. On a continuous straight line path oftravel of the sheet gripper mechanism, the sheet of support materialwould be uniformly pulled away from the surface of the drum in a linesubstantially parallel to the path of travel of the paper gripper and alineal speed equal to the peripheral speed of the Xerographic drum.This, of course, would require the use of a conveyor having a straightline run from the drum of a length at least equal to the length of thelargest sheet of support material to be transported by the sheetconveyor mechanism.

To reduce the overall size of the Xerographic apparatus,

a conveyor is used in the machine which has a straight run from the drumof a length less than the length of the largest sheet which can beconveyed by the sheet conveyor mechanism. Thus, in the apparatus shown,the trailing edge of a sheet of transfer material could still be incontact with the xerographic drum while the leading edge of the sheetcarried by the sheet gripper mechanism would be at the delivery stationof the apparatus.

As, shown by the rise position of the cams. 69., the sheet is carried bya sheet gripper mechanism which travels between delivery rollers 65 and66 and partly "around the sprockets 323 before the sheet, grippers areactuated by the cams to release the sheet.

In the apparatus shown, the position of each gripper 361 on the gripperbar, and the shape of each cam 69 to actuate the gripper are suchthatthe sheet is readily released. to be fed between the delivery rollers,65 and 66, rather than being fully carried around the axis of deliveryroller 65 by the sheet gripper mechanism. The sheet gripper mechanism issupported on the chains ina manner to allow the leading edge of thesheet gripper mechanism to be deflected outward as it travels around thesprockets 323 adjacent to the earns 69, while the trailing edge of thesheet gripper mechanism and therefore, the leading edge of the sheet ismaintained on a substantially uniform radius of rotation. about'thesprockets thereby keeping the lineal speed'of the paper uniform.

The sheet is carried'in this path until the grippers are opened by cams69 to release the sheet. As the grippers are actuated by the earns 69,to release the sheet, the jaws of the gripper are cammed upon in an arc.The radius of the grippers is a faster opening radius than the radiusof'the paper, as it tends to straighten, to preyent regripping of thepaper as the grippers are gripped again. As shown in FIG. 1, the leadingedge or" the paper would start to travel in an are around the sprockets,but as the leading edge of the sheet is released by the sheet grippermechanism, the elasticity of the paper will cause the leading edge ofthe sheet to snap up into a straight line into the plane of theremainder of the 8 sheet whereby the paper is discharged in a straightline path from th delivery rollers and 66.

It is apparent that a sheet gripper mechanism constructed in accordancewith the invention can be fabricated from relatively thin sheet metalstock material because of the novel configuration of the individualsheet gripper mechanisms and the particular configuration of the springwhich prevents warping or distortion of the sheet gripper, the springacting as a stiffener to the cam follower portion of each individualsheet gripper.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth. It isalso apparent that the term depending is used to describe the structure,as shown in the drawing, and this term is not used to limit thedefinition of the apparatus. This application is intended to cover suchmodifications or changes as may come within the purposes of theimprovements or the scope of the following claims.

What is claimed is: 1. In a sheet feeding apparatus having a pair ofconveyor chains adapted to transport a sheet gripper device from a sheetreceiving station to a sheet delivery station, wherein the sheetgripping device includes a gripper 'bar secured to said conveyor chainstransversely t-herebetween, sheet gripper jaw portion on said gripperbar serving as a common lower gripper jaw, and apertures and elongatedslots therein positioned between said gripper jaw portion and theleading edge of said gripper bar as determined by its direction oftravel as conveyed by said conveyer chains, a plurality of pins securedto the leading edge of said gripper bar, plurality of grippers pivotablysecured to said pins on said gripper bar, each of said grippers having acentrally located depending tang portion terminating in a curved-lipportion, said depending tang portion extending through one of saidelongated slots, jaw portions positioned on opposite sides of saiddepending central tang portion adapted to cooperate with said commonlower gripper jaw to grip the leading edge of a sheet therebetween, aplurality of springs, each of said springs being formed with a centralportion, coiled portions on opposite sides of the central portion andwith bent arms at opposite extremities thereof, each of said springsbeing mounted with its coiled portions encircling a pin on oppositesides of the gripper with which it cooperates and with the centralportion of the spring engaging the curved-lip portion of the gripper andwith the bent arm portions extending through apertures in the sheetgripper jaw portion to engage the underside of the gripper bar tonormally bias the grippers into cooperating relation with the lowergripper jaw,

and said depending tang portion, being adapted to be actuated by camslocated adjacent and between said conveyor chains at said sheetreceiving station and said sheet delivery station.

2. In a sheet feeding apparatus having a pair of conveyor chains adaptedto transport a sheet gripping mechanism from a sheet receiving stationto a sheet delivery station, 65

9 i@ a plurality of grippers pivotably secured by said pins thereof,each of said springs having its coiled porto said gripper bar, tionencircling one of said pins, the central portion each of said grippershaving jaw portions thereon engaging said curved-lip portion of saidgripper.

adapted to cooperate With said concave depressed 3. The apparatus ofclaim 2 wherein each of said pins portion of said gripper bar to gripthe leading edge 5 includes a central notched portion and each of saidgripof a sheet therebetween and a depending cam guide pers includes aspring tang extending into a central portion terminating in a curved-lipportion posinotched portion of one of said pins.

tioned to contact cams located adjacent and between said conveyor chainsat said sheet receiving station References flied by the Examiner andsaid sheet delivery station, 10 UNITED STATES PATENTS and springsoperatively connected to said gripper bar 1 543 374 6/25 Everett and tosaid grippers to normally bias said jaw por- 2374668 5/45 Davidsn tionsof said grippers into cooperative engagement 2500032 3/50 Halberg 24 66with said concave depressed portion of said grip- 2882049 4/59 Koch perjaw, ea h f said pr ng having n r p 15 3:100:109 8/63 Eichor; 270 79tion, coiled portions on opposite sides of said central portion and bentarms at opposite extremities ROBERT B. REEVES, Acting Primary Examiner.

1. IN A SHEET FEEDING APPARATUS HAVING A PAIR OF CONVEYOR CHAINS ADAPTEDTO TRANSPORT A SHEET GRIPPER DEVICE FROM A SHEET RECEIVING STATION TO ASHEET DELIVERY STATION, WHEREIN THE SHEET GRRIPPING DEVICE INCLUDES AGRIPPER BAR SECURED TO SAID CONVEYOR CHAINS TRANSVERSELY THEREBETWEEN, ASHEET GRIPPER JAW PORTION ON SAIGRIPPER BAR SERVING AS A COMMON LOWERGRRIPPER JAW, AND APERTURES AND ELONGATED SLOTS THEREIN POSITIONEDBETWEEN SAID GRIPPER JAW PORTION AND THE LEADING EDGE OF SAID GRIPPERBAR AS DETERMINED BY ITS DIRECTION OF TRAVEL AS CONVEYED BY SAIDCONVEYOR CHAINS, A PLURALITY OF PINS SECURED TO THE LEADING EDGE OF SAIDGRIPPER BAR, A PLURALITY OF GRIPPERS PIVOTABLY SECURED TO SAID PINS ONSAID GRIPPER BAR, EACH OF SAID GRIPPERS HAVING A CENTRALLY LOCATEDDEPENDING TANG PORTION TERMINATING IN A CURVED-LIP PORTION, SAI DDEPENDING TANG PORTION EXTENDING THROUGH ONE OF SAID ELONGATED SLOTS,JAW PORTIONS POSITIONED ON OPPOSITE SIDES OF SAID DEPENDING CENTRAL TANGPORTION ADAPTED TO COOPERATE WITH SAID COMMON LOWER GRIPPER JAW TO GRIPTHE LEADING EDGE OF A SHET THEREBETWEEN, A PLURALITY OF SPRINGS, EACH OFSAID SPRINGS BEING FORMED WITH A CENTRAL PORTION, COILED PORTIONNS ONOPPOSITE SIDES OF THE CENTTRAL PORTION AND WITH BENTT ARMS AT OPPOSITEEXTREMITIES THEREOF, EACH OF SAID SPRINGS BEING MOUNTED WITH ITS COILEDPORTIONS ENCIRCLING A PIN ON OPPOSITE SIDES OF THE GRIPPER WITH WHIC ITCOOPERATES AND WITH THE CENTRAL PORTION OF THESPRING ENGAGING THECURVED-LIP PORTION OF THE GRIPPER AND WITH THE BENT ARM PORTIONSEXTENDING THROUGH APERTURES IN THE SHEET GRIPPER JAW PORTION TO ENGAGETHE UNDERSIDE OF THE GRIPPER BAR TO NORMALLY BIAS THE GRIPPERS INTOCOOPERATING RELATION WITH THE LOWE GRIPPER JAW, AND SAID DEPENDING TANGPORTION BEING ADAPTED TO BE ACTUATED BY CAMS LOCATED ADJACENT ANDBETWEEN SAID CONVEYOR CHAINS AT SAID SHEET RECEIVING STATION AND SAIDSHEET DELIVERY STATION.